If any of you guys are running a USB UPS, and you see this error:
Can't claim POWERWARE USB interface: could not claim interface 0: Operation not permitted
Unable to find POWERWARE UPS device on USB bus (USB)

- check the permissions on that device to see if the "nut" group has access to it:
ls -l /dev/bus/usb/003/003
crw-rw-r-T 1 root root 189, 258 Dec 17 17:29 /dev/bus/usb/003/003

- chown it if needed: sudo chown root:nut /dev/bus/usb/003/003

- start up upsdrvctl again:
sudo upsdrvctl start

- start up nut:
sudo /etc/init.d/nut start

The device is identified properly in my /etc/udev/rules.d/52-nut-usbups.rules
file where it's supposedly to automatically configure that device to be accessible by the nut group, but doesn't after the D-U